Ecotoxicological assessment, oxidative response, and enzyme activity disorder of the rotifer Brachionus asplanchnoidis exposed to a toxic cocktail of spent lithium-ion battery leachate.

Spent lithium-ion batteries (LIBs) have emerged as a major source of waste due to their low recovery rate. The physical disposal of spent LIBs can lead to the leaching of their contents into the surrounding environment. While it is widely agreed that hazardous substances such as nickel and cobalt in the leachate can pose a threat to the environment and human health, the overall composition and toxicity of LIB leachate remain unclear. In this study, a chemical analysis of leachate from spent LIBs was conducted to identify its primary constituents. The ecotoxicological parameters of the model organism, rotifer Brachionus asplanchnoidis, were assessed to elucidate the toxicity of the LIB leachate. Subsequent experiments elucidated the impacts of the LIB leachate and its representative components on the malondialdehyde (MDA) level, antioxidant capacity, and enzyme activity of B. asplanchnoidis. The results indicate that both the LIB leachate and its components are harmful to individual rotifers due to the adverse effects of stress-induced disturbances in biochemical indicators, posing a threat to population development. The intensified poisoning phenomenon under combined stress suggests the presence of complex synergistic effects among the components of LIB leachate. Due to the likely environmental and biological hazards, LIBs should be strictly managed after disposal. Additionally, more economical and eco-friendly recycling and treatment technologies need to be developed and commercialized.

Toxic effects of microplastics and nitrite exposure on intestinal histology, digestion, immunity, and microbial community of shrimp Litopenaeus vannamei.

Nitrite and microplastics (MPs) are environmental pollutants that threaten intestinal integrity and affect immune function of shrimp. In this study, the shrimp Litopenaeus vannamei were exposed to the individual and combined stress of nitrite and microplastics for 14 days, and the changes of intestinal histology and physiological functions were investigated. After single and combined stress, affectations occurred in intestinal tissue; the antioxidant enzyme activities (MDA, H2O2, CAT increased) and gene expression levels (CAT, SOD, GPx, HSP70 up-regulated) changed. The expression levels of detoxification genes (CYP450, UGT down-regulated, GST up-regulated), apoptosis genes (CASP-3 up-regulated) and endoplasmic reticulum stress genes (Bip, GRP94 down-regulated) changed. Furthermore, the stress also increased intestinal microbial diversity, causing bacterial composition variation, especially beneficial bacteria and pathogenic bacteria. These results suggested that nitrite and microplastics stress had adverse effects on the intestinal health of L. vannamei by affecting intestinal tissue morphology, immune response and microbial community.

Toxic effects of three variants of microcystins on the intestinal histology, physiological and metabolic response of Litopenaeus vannamei.

Microcystins (MCs) are harmful substances to the health of cultured shrimp, and there are many variants of MCs. Intestinal is the immune and metabolic center of the shrimp, and is also the target organ for MCs toxicity. In this study, the shrimp Litopenaeus vannamei juvenile were separately exposed to 1 µg/L of three MCs variants (LR, YR, RR) for 72 h respectively, and the changes of intestinal morphology, physiological response and metabolic function were analyzed. The results showed the three MCs variants stress caused intestinal mucosal damage and disordered the homeostasis of antimicrobial genes (ALF and Lys) expression. The mRNA expression levels of antioxidant genes (Nrf2 and GPx) and apoptosis factors (CytC and Casp-3) were increased, but that of detoxification gene (CYP450) was decreased. Furthermore, the intestinal metabolic pattern was also influenced by stresses, among which MC-LR induced more differential metabolites than that of MC-YR and MC-RR. The function of purine metabolism was highly influenced by the stress of three MCs variants, followed by amino acid metabolism, but there were differences in the types of amino acids. The metabolites citric acid, L-glutamine, L-tryptophan, spermine, UMP, and indole contributed to the metabolic pathway network. Nineteen stress-related metabolites were identified as candidates for subsequent screening of potential biomarkers. These results revealed the toxic effects of three MCs variants on the intestinal physiological and metabolic homeostasis of the shrimp.

Toxic effects of triclocarban on the histological morphology, physiological and immune response in the gills of the black tiger shrimp Penaeus monodon.

Triclocarban (TCC) is a widely used broad-spectrum antimicrobial agent that has become a pollutant threatening the health of aquatic animals. However, the toxic effects of TCC on Penaeus monodon are still lacking. In this study, we exposed P. monodon to 1 µg/L (TCC-1) and 10 µg/L TCC (TCC-10) for 14 days, and the changes of histological morphology, physiological and immune responses in the gills were investigated. The results showed that TCC exposure caused the deformation of the gill vessels and the disordered arrangement of the gill filaments. Oxidative stress biochemical indexes such as H2O2 content, CAT and GPx activity and the relative expression levels of antioxidant-related genes (SOD, GPx and Nrf2) were increased in the TCC-1 and TCC-10 groups; the levels of CAT and HSP70 genes were increased but POD activity was decreased in the TCC-10 group. The relative expression levels of endoplasmic reticulum (ER) stress indexes such as ERP15 and ATF-6 genes were increased in the TCC-10 group, while the level of GRP78 gene was decreased in the TCC-1 and TCC-10 groups. The relative expression levels of apoptosis indexes such as p53 and JNK genes were increased, but CytC and Casp-3 genes were decreased in the TCC-1 and TCC-10 groups. Furthermore, the relative expression levels of detoxification metabolism-related genes (cytP450 and GST) and osmotic regulation-related genes (NKA-α, NKA-ß, CA, AQP, CLC and CCP) were increased in the TCC-10 group. The results showed that TCC exposure could affect the physiological homeostasis in the gills of P. monodon, probably via damaging histological morphology, inducing oxidative stress, and disordering ER stress, apoptosis, detoxification and osmotic regulation.

Integration of transcriptomic and metabolomic reveals carbonate alkalinity stress responses in the hepatopancreas of Litopenaeus vannamei.

Carbonate alkalinity (CA) is one of the environmental factors affecting the survival and growth of aquatic animals. However, the toxic effects of CA stress on Pacific white shrimp Litopenaeus vannamei at the molecular level are completely unclear. In this study, we investigated the changes of the survival and growth, and hepatopancreas histology of L. vannamei under different levels of CA stress, and integrated transcriptomics and metabolomics to explore major functional changes in the hepatopancreas and identify biomarkers. After CA exposure for 14 days, the survival and growth of the shrimp were reduced, and the hepatopancreas showed obvious histological damage. A total of 253 genes were differentially expressed in the three CA stress groups, and immune-related genes such as pattern recognition receptors, phenoloxidase system and detoxification metabolism were affected; substance transport-related regulators and transporters were mostly downregulated. Furthermore, the metabolic pattern of the shrimp was also altered by CA stress, especially amino acids, arachidonic acid and B-vitamin metabolites. The integration analysis of differential metabolites and genes further showed that the functions of ABC transporters, protein digestion and absorption, and amino acid biosynthesis and metabolism were highly altered by CA stress. The results of this study revealed that CA stress caused immune, substance transport, and amino acid metabolic variations in L. vannamei, and identified several potential biomarkers related to stress response.

Toxicity of titanium dioxide nanoparticles on the histology, liver physiological and metabolism, and intestinal microbiota of grouper.

Titanium dioxide nanoparticles (nano-TiO2) are a common environmental pollutant threatening aquatic animals. The natural habitats and cultured environments of groupers make them vulnerable to nanoparticle pollution. In this study, hybrid grouper juveniles were separately exposed to 1 or 10 mg/L nano-TiO2 for 14 days, and the toxicological response of these groupers were investigated. After nano-TiO2 exposure, the liver showed apparent histopathology and intestinal goblet cells were also affected. The transcription of antioxidant and apoptosis-related genes were down-regulated, and the inflammatory factor TNF-α was up-regulated in the liver. The metabolite patterns of the liver were disturbed, especially amino acid metabolism. The diversity and composition of the intestinal microbiota were also altered especially the genera Lactobacillus and Nautella. The changes of several intestinal bacteria were correlated with the immune factors and metabolites of respective hosts. We concluded that nano-TiO2 exposure negatively affects the physiological homeostasis of groupers.

Toxicological response of Pacific white shrimp Litopenaeus vannamei to a hazardous cyanotoxin nodularin exposure.

Nodularin (NOD) is a harmful cyanotoxin that affects shrimp farming. The hepatopancreas and intestine of shrimp are the main target organs of cyanotoxins. In this study, we exposed Litopenaeus vannamei to NOD at 0.1 and 1 µg/L for 72 h, respectively, and changes in histology, oxidative stress, gene transcription, metabolism, and intestinal microbiota were investigated. After NOD exposure, the hepatopancreas and intestine showed obvious histopathological damage and elevated oxidative stress response. Transcription patterns of immune genes related to detoxification, prophenoloxidase and coagulation system were altered in the hepatopancreas. Furthermore, metabolic patterns, especially amino acid metabolism and arachidonic acid related metabolites, were also disturbed. The integration of differential genes and metabolites revealed that the functions of "alanine, aspartic acid and glutamate metabolism" and "aminoacyl-tRNA biosynthesis" were highly affected. Alternatively, NOD exposure induced the variation of the diversity and composition of intestinal microbiota, especially the abundance of potentially beneficial bacteria (Demequina, Phyllobacterium and Pseudoalteromonas) and pathogenic bacteria (Photobacterium and Vibrio). Several intestinal bacteria were correlated with the changes of host the metabolic function and immune factors. These results revealed the toxic effects of NOD on shrimp, and identified some biomarkers.

Integration of metagenomic and metabolomic insights into the effects of microcystin-LR on intestinal microbiota of Litopenaeus vannamei.

Microcystin-LR (MC-LR) is a hazardous substance that threaten the health of aquatic animals. Intestinal microbes and their metabolites can interact with hosts to influence physiological homeostasis. In this study, the shrimp Litopenaeus vannamei were exposed to 1.0 µg/l MC-LR for 72 h, and the toxic effects of MC-LR on the intestinal microbial metagenomic and metabolomic responses of the shrimp were investigated. The results showed that MC-LR stress altered the gene functions of intestinal microbial, including ABC transporter, sulfur metabolism and riboflavin (VB2) metabolism, and induced a significant increase of eight carbohydrate metabolism enzymes. Alternatively, intestinal metabolic phenotypes were also altered, especially ABC transporters, protein digestion and absorption, and the biosynthesis and metabolism of amino acid. Furthermore, based on the integration of intestinal microbial metagenomic and metabolome, four bacteria species (Demequina globuliformis, Demequina sp. NBRC 110055, Sphingomonas taxi and Sphingomonas sp. RIT328) and three metabolites (yangonin, α-hederin and soyasaponin ii) biomarkers were identified. Overall, our study provides new insights into the effects of MC-LR on the intestinal microbial functions of L. vannamei.

Responses of lipid metabolism and lipidomics in the hepatopancreas of Pacific white shrimp Litopenaeus vannamei to microcystin-LR exposure.

Microcystin-LR (MC-LR) is a toxic substance that threatens the health of aquatic animals. Hepatopancreas is the target organ of MC-LR toxicity. In this study, we investigated the effects of MC-LR on hepatopancreas lipid metabolism and lipidomic responses in Litopenaeus vannamei. After MC-LR exposure for 72 h, the hepatopancreas showed obvious tissue damage, and the activities of several lipase isoenzymes were decreased. Furthermore, the relative gene expression levels of lipolysis (CPT1, AMPKα), lipogenesis (SREBP, FAS, ACC, 6PGD), and long-chain fatty acid ß-oxidation (ACDL, ACDVL, ACBP) were increased. MC-LR exposure also affected lipidomics homeostasis. Specifically, the levels of glycerophospholipids (phosphatidylcholine, phosphatidic acid, lyso-phosphatidylcholine, lyso-phosphatidylethanolamine, lyso-phosphatidylglycerol), sphingolipids (sphingomyelin and ceramides) and cholesteryl ester were increased, and those of phosphatidylinositol and triglyceride were decreased. The significantly altered lipid molecules were mainly associated with the pathways of lipid and fatty acid metabolism and autophagy. These results reveal that MC-LR exposure influences lipid metabolism and lipidomic homeostasis in the shrimp hepatopancreas.